Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a rotary positive
displacement internal combustion engine oE the type comprising
j two intermeshing rotors, each provided with a central hub
portion, amember ofaxially and radially extending spokelike lobes
with intervening grooves, andwithin itshub portion a central
channel system comprising a supply channel and a discharge
channel for passage of a cooling liquid therethrough.
More specifically the invention relates to means of
, such an engine providing an automatic circulation of the cooling
¦ 10 liquid in radial direction for transfer of the heat to be
removed radially inwardly to the central channel system owing
to the centrifugal forces acting upon two media of different
~ density.
; In rotors of complicated shape, especially such pro-
; vided with several relatively thin spokes extending from a
central hub it is a problem to circulate the cooling liquid
passing through the hub out into the back from the spokes in
order to obtain an efficient cooling of the spokes. One
~ example of such a rotor is a rotor of an internal combustion
i 20 engine of the type comprising two intermeshing rotors each
provided with grooves and intervening lands extending radially
inwardly from a generally cylindrical surface. An engine of
such a type is for instance shown in British patent 1 172 828.
In such a machine the lands of the rotors represent the spokes
'l mentioned above.
i Up to now it has been necessary to shape the rotors
with a complicated system of cooling channels to be passed
through by means of a forced pump circulation. Anyhow there
are difficulties to avoid pockets of stagnant liquid resulting
~ 30 in inadequate cooling of certain portions of the rotor lands.
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The pxesent inVention provides means Eor the internal
cooling of s~ch roto~s whlch means are efficient, simple and
inexpensive in production~
According to the present invention there is provided
a rotary positive di.splacement internal combustion engine of the
type comprising two intermeshin~ rotors, each provided with a
central hub portion, a plurality of axially and radially
extending spokeli]ce lobes with intervening grooves, and within
its huh portion a central channel system comprising a supply
channel and a discharge channel for passage of a cooling liquid
therethrough, at least one of the rotors within each of its
spokeli~e lobes being provided with at least one radially extend-
ing central channel having an inner end communicating with said
central supply channel and an outer end communicating with a
radially extending return passage connected to said cen-tral
discharge channel, said radially extending return passage bein~
interposed hetween said radially extending channel and each one
of said heated surface portions of said lobe to be cooled, said
raaially extending return passage and said radially extending :
channel heing composed of a cavity and a pipe, respectively, ~ :
said pipe being radially inserted in the cavity and projecting
from said central supply channel towards the radially outermost
portion of said ca~ity. Thus according to the present invention
at least one of the rotors within each of its spo~.elike lobes
is provided with at least one radially extending channel having
an inner end communicating with said central supply channel ~.
and an outer end communicating with a rad.ially extending return
. passage connected to said central discharge channel, said radially
I extending return passage being interposed said radially extendin~
channel and a heated surface portion of said lobe to be cooled.
, Since each return passage is interposed a radially extendingchannel and a flan}~ of the land so that the heat transerred from
the flank to the cooling liquid is supplied to -the li~uid in
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I the interposed passa~e onl~ the li~uid in the interposed
; passage will get a higher temperature than that in the radially
extending channel and consequently the density of the liauid
will be somewhat different in the two channels. The centrifugal
forces acting upon the liquid during revolving of the rotor
will then be different in the two channels resulting in an
j automatic circulation of the cooling liquid from the central
channel system outwardly through said set of radially extending
channels and inwardly back to the central channel system through
¦ 10 said set of interposed passages. Furthermore the higher the
3 temperature of the flank the larger the difference in density
between the ].i~uid in the two channels and conseauently the
speed of the radial circulation is increased which means that
i the capacity of the coolin~ automatically increases with an
increased supply of heat so that the temperature of the flank
j will be practically the same independant of the amount of heat
supplied to the surface of the rotor.
The present invention will be Eurther described by
way of the accompanying drawings, wherein;
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Figure 1 shows a cross section o~ a rotary abutment
member for a rotary internal combustion engine of the type
schematically indicated by dot-dashed lines.
Figure 2 shows a detail of Figure 1 on a larger scale,
and
I Figure 3 shows a longitudinal section o~ the rotor
¦ detail shown in Figure 2.
;~ The engine indicated by dot-dashed lines in Figure 1
-' has a casing 1 enclosing a working space composed of the barrel
walls of two intersecting bores 2, 3 having paral].el axes and
intersecting along two straight axial lines and two end walls.
The casing 1 is provided with combined inlet and scavenging
outlet channels 4 and with exhaust ports 5, 6 in the barrel
, walls of the two intersecting bores 2, 3 and further with a
; fuel injection nozzle 7 and a spark plug 8 placed in a somewhat -
depressed position in each of the three tip portions of a power
rotor 9 which is rotatably mounted in the casing 1 for sealing
cooperation with the walls of the bore 2.
~ A rotary abutment me~ber or abutment rotor 10 is
;' 20 rotatably mounted in the casing 1 for sealing cooperation with
the walls of the bore 3 and with the power rotor 9 as is clearly
, described in the British patent specification 1 392 174. The
abutment rotor 10 is provided with five grooves 12 and inter-
vening lands 1~ extending axially along the rotor. As better :
shown in Figures 2 and 3 the rotor 10 is provided with a central,
axially extending bore 16 in which a concentric pipe 18 is
,~inserted. A cooling liquid is in a conventional manner supplied
to the pipe 18 and discharged from the bore 16 outside the
.1 pipe 18~ Each land 14 of the rotor 10 is furthex provided with
five axially spaced bores 20 extending radially outwards from
the central bore 16. A pip2 22 is inserted in each radial. bore
~;
20 and is supported in its outer end by the bottom of the bore
20, whereas its inner end penetrates the central pipe 18 and is
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supported thereby. The outer end of the pipe 22 ls further
provided with slits 24 in order to form a communication between
the pipe 22 and the surrounding bore 20.
The internal cooling of the rotor 10 takes place in
-I the following way. The cooling liquid, for instance water or
~ oil, is supplied to the central pipe 18 from an outer source,
¦ not shown, of cooling liquid and fills up the channel system,
comprising the central pipe 18, the radial pipes 22, the radial
bores 20, and the central bore 16, and i9 discharged from the
central bore 16 through a cooler, not shown, back to the liquid
source. During operation of the engine the rotor 10 is contin-
uously revolved at a high speed, simultaneously as the flanks
and the crest of each ro~or land 14 is exposed to the high ~-~
temperature of the wor~ing fluid passing through the engine.
Owing to the centrifugal forces the cooling liquid will be
forced outwardly through the radial pipes 22 and the radial
bores 20. The heat absorbed by the surfaces of the rotor land
14 from the hot working fluid is transferred through the body of
the land 14 to the surface of each radial bore 20, and further
transferred to the liquid in the bore 20 contacting said surface.
The liquid in thebore 20 outside the pipe 22 will in this way
get a higher temperature than that of the liquid inside the pipe
22. Owing to the temperature difference the density of the
liquid outside the pipe 22 will be lower than that inside the ~;
i pipe 22. Consequently the centrifugal forces acting upon the
~- liquid outside and inside the bore 22 will not any longer be
the same, but the forces acting upon the liquid outside the
pipe 22 will decrease those inside the pipe 22 resulting in a
forced circulation outwardly inside the pipe 22 and inwardly
outsid~ the pipe 22. In other words an automatic circulation of
the cooling liquid through the radial channel system is achieved.
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~l This automatic circulation effect can be taken care of
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in different ways.
The simplest way is to completely rely upon this
effect which means that no pump is needed for the circulation of
the liquid from the back to the liquid source.
However, in most cases a pump for the circulation is
needed to speed up the flow in spite of the flow losses in the
system including the liquid cooler, which otherwise must be
considerably larger. In such a pump circulation system the
automatic circulation effect is of extremely importance not only
to the resulting decrease of the power needed for the pump, but
primarily as it guarantees such a distribution of the liquid
, that more liquid is distributed to those portions of the rotor
4 14 where the temperautre is higher than to those portions there-
of where the temperature is lower. The cooling effect is thus
,~ so distributed inside the rotor that not only the different
lands 14 will be kept at about the same temperature, but also
I ~ the different axial sections of each land 14 will be kept at
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practically the same temperature. In other words the invention
results in a guarantee that no portion is overheated without
~ ~ 20 any risk that any other part thereof is cooled down to a non-
; ~ desired low temperature resulting in a disadvantageous increase of the cooling losses of the engine.
;~ When using a pump circulation system a direct communi-~ cation between the central pipe 18 and the surrounding bore 16
,l may be advantageous for reduction of the cooling effect at part.,. , ,
load of the engine, and if the cooling liquid passes axially
through the rotor 10 from an inlet in one end thereof to an out-
let in the other end thereof the central pipe 18 may be complet-
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ely dispensed with.
;30 One or both rotors 9j 10 may be provided with means
~i for cooling the rotors. If the interspaces between the bore 20
;1 and the adjacent surfaces of the land 14 in Figure 2 is not too
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narrow it is possible to use the bore 20 in substitute for said
radially extending channel 22 and to provide each land 14 with
radially extending return bores on opposite sides of each bore
20 adjacent the surfaces of the lands 14, the outer ends of each
bore 20 and adjacent return bores being connected to each other
via suitable circumferential passages.
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